This invention relates to the packaging of integrated-circuit chips and, more particularly, to an assembly for mounting a chip on a printed-circuit board.
Various solutions have been proposed to the problem of connecting a microminiature integrated-circuit chip to a standard printed-circuit board. In accordance with one approach, the chip is mounted in the recessed portion of the top side of a so-called flat-pack carrier that contains a radially extending conductive pattern. Wire bonds extend between pads on the chip and inner terminal portions of the conductive pattern. A protective material and/or a cover are typically added to the carrier to seal the mounted chip in place. After sealing, outer terminal portions of the conductive pattern on the carrier remain accessible for interconnection to an associated electrical component such as a printed-circuit board.
Several known approaches are then available for mounting the flat-pack-packaged chip on a printed-circuit board. In one approach, the carrier is placed top-side down on a board that includes a conductive pattern with solder bumps. The bumps are located to establish respective electrical contact with the outer terminal portions of the conductive pattern on the carrier. In another approach, the carrier is bonded top-side up to a printed-circuit board that includes conductive terminal portions formed on the board in the immediate vicinity of the bonded carrier. Wire bonds are then made between these terminal portions on the board and the outer terminal portions of the conductive pattern on the carrier.
For some applications, the aforementioned approaches are adequate for mounting a chip-containing carrier on a printed-circuit board. But soldered or bonded carriers on a printed-circuit board cannot easily be replaced during development and testing of the board. Additionally, the final-design version of such a board cannot easily be repaired in the field.
Accordingly, workers in the art have directed considerable efforts at trying to devise other approaches for mounting flat-pack-packaged chips on a printed-circuit board. It was recognized that such efforts, if successful, had the potential for providing an improved mounting assembly capable of lowering the cost of developing, testing and repairing equipment that includes chip carriers on a printed-circuit board.